[Bug middle-end/102580] Failure to optimize signed division to unsigned division when dividend can't be negative

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102580

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aldyh at gcc dot gnu.org,
                   |                            |amacleod at redhat dot com,
                   |                            |jakub at gcc dot gnu.org

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
To be precise, expand_expr_divmod uses get_range_pos_neg for that during
expansion (unless we'd e.g. somehow noted it in some very late pass before
expansion that the division ought to be expanded both ways and cost compared),
and get_range_pos_neg uses the global range of SSA_NAME only.  In order to
optimize #c0 we'd need to query range with the use stmt and enabling ranger in
the pass (that is possible in some pass before expansion, but doing it during
expansion (which would be useful to other spots too, say .*_OVERFLOW expansion)
would need to deal with some basic blocks already converted into RTL and others
still at GIMPLE).